title: Reduction of effective dose and organ dose to the eye lens in head MDCT using iterative image reconstruction and automatic tube current modulation.
abstract: OBJECTIVE
  To compare the effective and eye lens radiation dose in helical MDCT brain examinations using automatic tube current modulation in conjunction with either standard filtered back projection (FBP) technique or iterative reconstruction in image space (IRIS).
  
  
  METHODS
  Of 400 adult brain MDCT examinations, 200 were performed using FBP and 200 using IRIS with the following parameters: tube voltage 120 kV, rotation period 1 second, pitch factor 0.55, automatic tube current modulation in both transverse and longitudinal planes with reference mAs 300 (FBP) and 200 (IRIS). Doses were calculated from CT dose index and dose length product values utilising ImPACT software; the organ dose to the lens was derived from the actual tube current-time product value applied to the lens. Image quality was assessed by two independent readers blinded to the type of image reconstruction technique.
  
  
  RESULTS
  The average effective scan dose was 1.47±0.26 mSv (FBP) and 0.98±0.15 mSv (IRIS), respectively (33.3% decrease). The average organ dose to the eye lens decreased from 40.0±3.3 mGy (FBP) to 26.6±2.0 mGy (IRIS, 33.5% decrease). No significant change in diagnostic image quality was noted between IRIS and FBP scans (P=0.17).
  
  
  CONCLUSIONS
  Iterative reconstruction of cerebral MDCT examinations enables reduction of both effective and organ eye lens dose by one third without signficant loss of image quality.
authors.affiliation: Department of Radiology, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Ryska
authors.forename: Tomas
authors.initials: T
authors.lastname: Kvasnicka
authors.forename: Jiri
authors.initials: J
authors.lastname: Jandura
authors.forename: Ludovit
authors.initials: L
authors.lastname: Klzo
authors.forename: Jakub
authors.initials: J
authors.lastname: Grepl
authors.forename: Jan
authors.initials: J
authors.lastname: Zizka
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007908:Lens, Crystalline; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D011446:Prospective Studies; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio